CD44 and cancer: By incorporating ligands of cancer biomarker proteins integrins and heparan sulfate proteoglycans (HSPGs) into the assembly building blocks (Figure 1b),[12] we developed assembling ligands P1 and P2 (Figure 1c).[13] Through PBIPA, both ligands self‐assemble forming extracellular scaffolds selectively adhere to the apical membrane of cancer cells.